During an immunoassay or the like, an analyte (a substance to be analyzed) is measured quantitatively by analyzing an antigen-antibody reaction. This is typically done by the following procedure. First, a sample containing the analyte is mixed with magnetic particles, an antibody including a labeled substance, and an antibody that binds the magnetic particles to the analyte, thereby causing an antigen-antibody reaction. Then, a magnetic separator is used to capture the resultant substance formed by the binding between the analyte, the magnetic particles, and the labeled substance. Thereafter, a voltage is applied to the captured substance to measure its luminescence value. Such a chemical analysis often requires the use of an automated analyzer.
An example of such an automated analyzer is the one disclosed in Japanese Patent No. 2955613 (Patent Document 1). This automated analyzer uses one set of reagent vessels for each sample analysis. One reagent vessel set consists of three reagent vessels: a vessel that contains a solution including magnetic particles; a vessel that contains a solution including a labeled substance; and a vessel that contains a solution including an antibody. Each of the reagent vessels has a lid so as to prevent reagent evaporation or deterioration.